This invention relates to controllers for high magnitude potential sources used in, for example, electrostatically aided coating material atomization and dispensing devices. Many such systems are known. There are, for example, the systems illustrated and described in U.S. Pat. Nos. 3,851,618; 3,875,892; 3,894,272; 4,075,677; 4,187,527; 4,324,812; 4,481,557; 4,485,427; 4,745,520; and, 5,159,544, to identify but a few.
According to the invention, a high magnitude potential supply comprises a first circuit for generating a first signal related to a desired output high magnitude potential across a pair of output terminals of the supply, a second circuit for generating a second signal related to an output current from the high magnitude potential supply, and a third circuit for supplying an operating potential to the high magnitude potential supply so that it can produce the high magnitude operating potential. The third circuit has a control terminal. A fourth circuit is coupled to the first and second circuits and to the control terminal. The fourth circuit receives the first and second signals from the first and second circuits and controls the operating potential supplied to the high magnitude potential supply by the third circuit. A fifth circuit is provided to selectively disable the supply of operating potential to the high magnitude potential supply so that no high magnitude operating potential can be supplied by it. The fifth circuit is also coupled to the control terminal.
Illustratively, the first and second circuits comprise a programmable logic controller (PLC), and a high speed bus for coupling the PLC to the fourth circuit.
Additionally illustratively, the first and second circuits respectively comprise first and second potentiometers for selecting a desired output high magnitude potential and output current, respectively, and conductors for coupling the first and second potentiometers to the fourth circuit.
Further illustratively, first and second switches selectively couple one of the PLC and the first potentiometer, and one of the PLC and the second potentiometer, respectively, to the fourth circuit.
Additionally illustratively according to the invention, the third circuit comprises a high magnitude potential transformer having a primary winding and a secondary winding. The primary winding has a center tap and two end terminals. Third and fourth switches are coupled to respective ones of the end terminals. A source of oppositely phased first and second switching signals controls the third and fourth switches, respectively.
Illustratively, the fourth circuit comprises a switching regulator having an input terminal forming a summing junction for the first signal and the second signal and a output terminal coupled to the center tap. The fifth circuit includes a microprocessor (xcexcP) and a fifth switch coupled to the xcexcP to receive a third switching signal from the xcexcP. The fifth switch is coupled to the summing junction to couple the third switching signal to the switching regulator to disable the supply of operating potential to the center tap.
Illustratively, the fifth switch is coupled to the summing junction through a filter which smooths the switching signals generated by the fifth switch in response to the xcexcP""s control.
Further illustratively, the apparatus comprises a sixth circuit cooperating with the xcexcP to determine if operating potential is being supplied to the high magnitude potential supply, and a seventh circuit cooperating with the xcexcP to determine if the high magnitude potential supply is indicating that it is generating high magnitude potential. The xcexcP indicates a fault if the operating potential is not being supplied to the high magnitude potential supply and the high magnitude potential supply is indicating that it is generating high magnitude potential. Illustratively, the xcexcP also indicates a fault if the operating potential is being supplied to the high magnitude potential supply and the high magnitude potential supply is indicating that it is not generating high magnitude potential.